A. Elhaddaoui et al., SPECTROSCOPIC INVESTIGATIONS OF SYNTHETIC BETA-AMYLOID PEPTIDES OF ALZHEIMERS-DISEASE, Journal of molecular structure, 347, 1995, pp. 363-369
The chemical mechanism of binding between Congo red dye and amyloid pr
oteins was investigated using infrared spectroscopy. Synthetic amyloid
corresponding to the amino-acid residues 1 to 28 of Alzheimer's beta
amyloid and insulin fibers prepared with the Burke and Rougvie method
were used as substrates. Both peptides clearly demonstrate beta-pleate
d sheet conformations. The analysis shows that Congo red binds to amyl
oid proteins via interactions between the two negatively-charged sulfo
nic acid groups of Congo red and two positively charged amino acid res
idues of amyloid protein molecules. Evidence leads to the conclusion t
hat the beta-pleated sheet conformation of the protein aids in orienti
ng the dye molecules, thus favoring stabilisation and bonding.